U.S. patent application number 15/025182 was filed with the patent office on 2016-08-11 for syntactic polyurethane elastomer based on soft segment prepolymer and non-mercury catalyst for use in subsea pipeline insulation.
The applicant listed for this patent is DOW GLOBAL TECHNOLOGIES LLC. Invention is credited to Mark Brown, II, Mikhail Y. Gelfer, Amber Stephenson.
Application Number | 20160229978 15/025182 |
Document ID | / |
Family ID | 53004962 |
Filed Date | 2016-08-11 |
United States Patent
Application |
20160229978 |
Kind Code |
A1 |
Gelfer; Mikhail Y. ; et
al. |
August 11, 2016 |
SYNTACTIC POLYURETHANE ELASTOMER BASED ON SOFT SEGMENT PREPOLYMER
AND NON-MERCURY CATALYST FOR USE IN SUBSEA PIPELINE INSULATION
Abstract
Syntactic polyurethane elastomers are made using a non-mercury
catalyst. The elastomer is made from a reaction mixture containing
a prepolymer made from a polyether polyol and a polyisocyanate, a
chain extender, a polyisocyanate and microspheres. The elastomer
adheres well to itself, which makes it very useful as thermal
insulation for pipelines and other structures that have a complex
geometry.
Inventors: |
Gelfer; Mikhail Y.;
(Sugarland, TX) ; Stephenson; Amber; (Lake
Jackson, TX) ; Brown, II; Mark; (Richwood,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DOW GLOBAL TECHNOLOGIES LLC |
Midland |
MI |
US |
|
|
Family ID: |
53004962 |
Appl. No.: |
15/025182 |
Filed: |
October 21, 2014 |
PCT Filed: |
October 21, 2014 |
PCT NO: |
PCT/US14/61605 |
371 Date: |
March 25, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61897359 |
Oct 30, 2013 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 9/32 20130101; C08G
18/10 20130101; C08G 18/3206 20130101; C08G 18/7657 20130101; C08L
75/04 20130101; C08L 75/04 20130101; C08K 7/28 20130101; C08G
18/4841 20130101; C09D 175/08 20130101; F16L 59/14 20130101; B05D
7/52 20130101; C08G 18/10 20130101; C08J 2375/08 20130101; C08G
18/7671 20130101; B05D 3/007 20130101; C08G 18/222 20130101; C08J
2375/04 20130101; C08G 18/3206 20130101; C08K 7/28 20130101; C08L
75/04 20130101; C08K 7/28 20130101 |
International
Class: |
C08J 9/32 20060101
C08J009/32; C08G 18/48 20060101 C08G018/48; C08G 18/22 20060101
C08G018/22; B05D 3/00 20060101 B05D003/00; C09D 175/08 20060101
C09D175/08; F16L 59/14 20060101 F16L059/14; B05D 7/00 20060101
B05D007/00; C08G 18/76 20060101 C08G018/76; C08K 7/28 20060101
C08K007/28 |
Claims
1. A method for making a syntactic polyurethane elastomer,
comprising a) forming a reaction mixture containing an alkylene
glycol chain extender, 5 to 50 weight percent, based on the weight
of the reaction mixture, of microspheres, an isocyanate-terminated
prepolymer having an isocyanate content of 3 to 12% by weight, and
a non-mercury catalyst, wherein (i) the prepolymer is the reaction
product of at least one polyether polyol having a number average
hydroxyl equivalent weight of at least 800 with an excess of an
aromatic polyisocyanate, (ii) the amount of prepolymer provided to
the reaction mixture is sufficient to provide an isocyanate index
of 80 to 130, (iii) wherein the non-mercury catalyst is a zinc
carboxylate or a mixture of 98-99.99 weight percent of one or more
zinc carboxylates and 0.01 to 2 weight percent of one or more
zirconium carboxylates and (iv) the reaction mixture is essentially
devoid of mercury compounds, and b) curing the reaction mixture to
form the syntactic polyurethane elastomer.
2. The process of claim 1 wherein in step b) is performed on the
surface of a substrate to form a coating of the syntactic
polyurethane elastomer on the substrate.
3. A process for producing a substrate having an applied syntactic
polyurethane elastomer, comprising a) forming a section of a
syntactic polyurethane elastomer on at least a portion of the
substrate by (1) applying a first reaction mixture containing an
alkylene glycol chain extender, 5 to 35 weight percent, based on
the weight of the reaction mixture, of microspheres, an
isocyanate-terminated prepolymer having an isocyanate content of 3
to 12% by weight, and a non-mercury catalyst, wherein (i) the
prepolymer is the reaction product of at least one polyether polyol
having a number average hydroxyl equivalent weight of at least 800
with an excess of an aromatic polyisocyanate, (ii) the amount of
prepolymer provided to the reaction mixture is sufficient to
provide an isocyanate index of 80 to 130, (iii) wherein the
non-mercury catalyst is a zinc carboxylate or a mixture of 98-99.99
weight percent of one or more zinc carboxylates and 0.01 to 2
weight percent of one or more zirconium carboxylates and (iii) (iv)
the reaction mixture is essentially devoid of mercury compounds, to
at least a portion of the substrate and (2) at least partially
curing the first reaction mixture to form the first section of
syntactic polyurethane elastomer, and then b) forming a second
section of syntactic polyurethane elastomer on at least a portion
of the substrate by (1) applying a second reaction mixture
containing an alkylene glycol chain extender, 5 to 35 weight
percent, based on the weight of the reaction mixture, of
microspheres, an isocyanate-terminated prepolymer having an
isocyanate content of 3 to 12% by weight, and a non-mercury
catalyst, wherein (i) the prepolymer is the reaction product of at
least one polyether polyol having a number average hydroxyl
equivalent weight of at least 800 with an excess of an aromatic
polyisocyanate, (ii) the amount of prepolymer provided to the
reaction mixture is sufficient to provide an isocyanate index of 80
to 130, (iii) wherein the non-mercury catalyst is a zinc
carboxylate or a mixture of 98-99.99 weight percent of one or more
zinc carboxylates and 0.01 to 2 weight percent of one or more
zirconium carboxylates and (iii) (iv) the reaction mixture is
essentially devoid of mercury compounds to at least a portion of
the substrate and in contact with the first section of syntactic
polyurethane elastomer to form at least one bondline between the
first section of syntactic polyurethane elastomer and the second
reaction mixture and (2) at least partially curing the second
reaction mixture to form the second section of syntactic
polyurethane elastomer adherent to the first section of syntactic
polyurethane elastomer.
4. The process of claim 3 wherein the bondline has a bond strength
of at least 8.0 MPa.
5. The process of claim 4 wherein the bondline has no visible
defects when visualized microscopically at a magnification of
100.times..
6. The process of claim 3 wherein the substrate is an undersea pipe
or undersea architecture.
7. The process of claim 6 wherein the undersea pipe or undersea
architecture is branched, curved or has another non-linear
configuration.
8. The process of claim 6 wherein the undersea pipe or undersea
architecture has one or more external features that protrude
partially or completely through the applied syntactic polyurethane
elastomer.
9. The process of claim 3, wherein the polyether polyol used to
make the isocyanate-terminated prepolymer is prepared by (A) adding
propylene oxide and ethylene oxide to a difunctional or
trifunctional initiator to produce a polyol having a hydroxyl
equivalent weight of 1500 to 2500 and containing 5 to 30% by weight
polymerized ethylene oxide, wherein the polymerized ethylene oxide
is randomly polymerized with the propylene oxide, forms one or more
internal blocks and/or forms terminal blocks that result in primary
hydroxyl groups or (B). homopolymerizing propylene oxide or
randomly copolymerizing 75-99.9 weight percent propylene oxide and
0.1 to 25 weight percent ethylene oxide onto a trifunctional
initiator, and optionally capping the resulting polyether with up
to 30% by weight (based on total product weight) ethylene oxide to
form a polyether polyol having an equivalent weight of 1500 to
2500.
10. The process of claim 9, wherein the chain extender is
1,4-butanediol.
11. (canceled)
12. The process of claim 3 wherein each respective reaction mixture
contains 15 to 25 weight percent microspheres.
13 (canceled)
Description
[0001] This invention relates to syntactic polyurethane elastomers
useful as subsea pipe and architecture insulation.
[0002] Subsea pipelines are used globally to deliver petroleum
and/or natural gas from subsea wellhead collection facilities at
the ocean surface. Cold sea temperatures can cause solid waxes and
hydrates to form as the production fluids are pumped to the
surface. This problem is ameliorated by applying a
thermally-insulating layer to the exterior of the pipe.
[0003] Rigid polyurethane foams are widely used as thermal
insulation. These are commonly made by reacting a polyisocyanate
with a curing agent in the presence of a blowing gas. The blowing
gas becomes trapped in cells in the foam. The trapped gas is
largely responsible for the thermal insulation properties of the
foam. In most applications, the polyurethane insulating foams are
rigid materials. However, a highly rigid polyurethane is unsuitable
as subsea pipeline insulation, because its mechanical strength is
not sufficient to withstand high pressures typically encountered in
subsea applications. The foam densifies and can collapse under the
pressure of the seawater, and the densified material is a poor
thermal insulator. In addition, the material is too brittle to
withstand bending the pipeline undergoes during production,
installation and use. An elastomeric insulating material is
needed.
[0004] Therefore, so-called "syntactic" elastomers have been
developed for the subsea pipeline applications. The syntactic
elastomers contain hollow microspheres embedded in an elastomeric
polyurethane matrix. The microspheres are generally made of glass
or other hard material that can withstand the high undersea
pressures.
[0005] The polyurethane matrix is a reaction product of a
polyisocyanate, a "polyol" component and a "chain extender". The
"polyol" is typically a polyether having 2 to 4 hydroxyl groups and
an equivalent weight per hydroxyl group of 1000 to 6000. The "chain
extender" is typically a diol having an equivalent weight of up to
about 125. 1,4-butanediol is the most commonly used chain extender
in these applications. The polyol, chain extender and
polyisocyanate are mixed and cured in the presence of the
microspheres to form the syntactic foam.
[0006] The curing reaction requires a catalyst to obtain reasonable
production rates. For decades, the catalyst of choice has been an
organomercury type, phenylmercury neodecanoate. This organomercury
catalyst has many benefits. It provides a very useful curing
profile. Reaction systems containing this organomercury catalyst
react slowly at first and build viscosity gradually for a period of
time. This characteristic provides valuable "open time", during
which the reaction mixture can be degassed and introduced into the
mold or other place where it is to be cured. After this slow
initial cure, the polymerization rate accelerates, so curing times
are reasonably short.
[0007] Polyurethanes made using organomercury catalysts also have
very good physical properties.
[0008] The organomercury catalysts are coming under regulatory
pressure, and there is now a desire to replace them with different
catalysts. Although a very wide range of materials is known to
catalyze the curing reaction, it has proven to be very difficult to
duplicate the performance of the organomercury catalysts. Many
catalysts fail to provide the favorable curing profile of
organomercury catalysts. Even when the curing profile can be
approximated using alternative catalysts, the good physical
properties obtained using organomercury catalysts have proven to be
difficult to duplicate.
[0009] One catalyst that has found use in syntactic polyurethane
elastomer applications is a mixture of a zinc carboxylate and a
small amount of a zirconium carboxylate. This catalyst provides a
curing profile similar to, but not quite beneficial as, the
organomercury catalysts. However, a very significant and previously
unknown problem has been found when using this catalyst. The
applied syntactic elastomer tends to crack. The cracking problem
can be quite pronounced when the substrate has a complex exterior
geometry such as when the substrate is branched or contains
external surface features.
[0010] Another problem seen when using non-organomercury catalysts
is that the polyurethane does not bond well to itself. This is a
very significant shortcoming. It is common to apply the thermal
insulation in multiple layers or to apply the thermal insulation to
different portions of the substrate at different times. A bondline
is formed where the separate layers or sections come into contact.
Even when a single layer of polyurethane insulation is applied,
bondlines form when the reaction mixture divides into multiple flow
fronts as it flows around the part and the separate flow fronts
meet. When the polyurethane does not adhere to itself very
strongly, cracks appear at the bondlines. This leads to a loss of
thermal insulation efficiency and can expose the underlying
substrate to the corrosive effects of seawater.
[0011] What is needed in the art is a method of making a syntactic
polyurethane elastomer, which does not contain a mercury catalyst,
which is resistant to cracking even when cast in confined complex
geometries and which bonds well to itself.
[0012] This invention is in one aspect a cured syntactic
polyurethane elastomer which is a reaction product of a reaction
mixture comprising an alkylene glycol chain extender, 5 to 50
weight percent, based on the weight of the reaction mixture, of
microspheres, an isocyanate-terminated prepolymer having an
isocyanate content of 3 to 12% by weight, and a non-mercury
catalyst, wherein (i) the prepolymer is the reaction product of at
least one polyether polyol having a number average hydroxyl
equivalent weight of at least 800 with an excess of an aromatic
polyisocyanate, (ii) the amount of prepolymer provided to the
reaction mixture is sufficient to provide an isocyanate index of 80
to 130, and (iii) the reaction mixture is essentially devoid of
mercury compounds.
[0013] The invention is also a method for making a syntactic
polyurethane elastomer, comprising
[0014] a) forming a reaction mixture containing an alkylene glycol
chain extender, 5 to 50 weight percent, based on the weight of the
reaction mixture, of microspheres, an isocyanate-terminated
prepolymer having an isocyanate content of 3 to 12% by weight, and
a non-mercury catalyst, wherein (i) the prepolymer is the reaction
product of at least one polyether polyol having a number average
hydroxyl equivalent weight of at least 800 with an excess of an
aromatic polyisocyanate, (ii) the amount of prepolymer provided to
the reaction mixture is sufficient to provide an isocyanate index
of 80 to 130, and (iii) the reaction mixture is essentially devoid
of mercury compounds, and
[0015] b) curing the reaction mixture to form the syntactic
polyurethane elastomer.
[0016] Surprisingly, the syntactic polyurethane elastomer of the
invention is morphologically very similar to conventional syntactic
polyurethane elastomers made in a one-step process (i.e., without
first forming a prepolymer by reacting the starting polyisocyanate
with the polyol) using a mercury catalyst. These morphological
similarities are seen using microscopic methods such as atomic
force microscopy (AFM) as described more fully below. The syntactic
polyurethane elastomer contains small discrete morphological
domains of the order of 0.1 to 3 .mu.m in diameter and is
substantially free of discrete morphological domains on the order
of 5 to 30 .mu.m in diameter. These small discrete morphological
domains are believed to represent regions rich in "hard segment",
i.e., the reaction product of the polyisocyanate and chain
extender. Similarly sized discrete morphological domains are seen
in conventional processes, using a mercury catalyst and without
forming the prepolymer. When using a non-mercury catalyst without
forming the prepolymer, the polyurethane often contains many large
discrete morphological domains that are of the order of 5 to 30
.mu.m across. It is believed that the morphological differences
account at least in part for the difference in performance of
elastomers made using mercury catalysts vs. non-mercury catalysts.
The morphology of the Hg-GSPU systems correlates to better residual
stress and shrinkage profile with acceptable application
properties. The ability to simulate the morphology obtained with
mercury-catalyzed systems without using a mercury catalyst is
unexpected and quite advantageous.
[0017] The syntactic polyurethane elastomer of this invention also
exhibits mechanical properties quite similar to those of
conventional syntactic polyurethane elastomers made in the
conventional one-step process with a mercury catalyst.
[0018] The process of the invention is suitable for applying a
syntactic polyurethane elastomer to a substrate. Substrates of
interest are parts that require thermal insulation. Subsea pipe and
subsea architecture are substrates of particular interest.
[0019] An important advantage of this invention is that the
syntactic polyurethane elastomer bonds well to itself and to other
cured polyurethane elastomers. Thus, in certain embodiments, the
invention is a process for producing a substrate having an applied
syntactic polyurethane elastomer to a substrate. This process
comprises the steps of
[0020] a) forming a section of a syntactic polyurethane elastomer
on at least a portion of the substrate by (1) applying a first
reaction mixture containing an alkylene glycol chain extender, 5 to
35 weight percent, based on the weight of the reaction mixture, of
microspheres, an isocyanate-terminated prepolymer having an
isocyanate content of 3 to 12% by weight, and a non-mercury
catalyst, wherein (i) the prepolymer is the reaction product of at
least one polyether polyol having a number average hydroxyl
equivalent weight of at least 800 with an excess of an aromatic
polyisocyanate, (ii) the amount of prepolymer provided to the
reaction mixture is sufficient to provide an isocyanate index of 80
to 130, and (iii) the reaction mixture is essentially devoid of
mercury compounds, to at least a portion of the substrate and (2)
at least partially curing the first reaction mixture to form the
first section of syntactic polyurethane elastomer, and then
[0021] b) forming a second section of syntactic polyurethane
elastomer on at least a portion of the substrate by (1) applying a
second reaction mixture containing an alkylene glycol chain
extender, 5 to 35 weight percent, based on the weight of the
reaction mixture, of microspheres, an isocyanate-terminated
prepolymer having an isocyanate content of 3 to 12% by weight, and
a non-mercury catalyst, wherein (i) the prepolymer is the reaction
product of at least one polyether polyol having a number average
hydroxyl equivalent weight of at least 800 with an excess of an
aromatic polyisocyanate, (ii) the amount of prepolymer provided to
the reaction mixture is sufficient to provide an isocyanate index
of 80 to 130, and (iii) the reaction mixture is essentially devoid
of mercury compounds to at least a portion of the substrate and in
contact with the first section of syntactic polyurethane elastomer
to form at least one bondline between the first section of
syntactic polyurethane elastomer and the second reaction mixture
and (2) at least partially curing the second reaction mixture to
form the second section of syntactic polyurethane elastomer
adherent to the first section of syntactic polyurethane
elastomer.
[0022] FIG. 1 is dynamic mechanical analysis curve for an
embodiment of the invention.
[0023] FIG. 2a) is a micrograph of a syntactic polyurethane
elastomer of the invention.
[0024] FIG. 2b) is a micrograph of a prior art syntactic
polyurethane elastomer.
[0025] FIG. 2c) is a micrograph of a prior art syntactic
polyurethane elastomer.
[0026] For purposes of this invention, a chain extender is one or
more compounds having two to three hydroxyl groups and a hydroxyl
equivalent weight of up to 125. A preferred type of chain extender
is an aliphatic glycol or glycol ether. The aliphatic glycol is a
straight-chain or branched alkane having two hydroxyl groups. The
glycol ether is a straight-chain or branched aliphatic ether or
polyether. The hydroxyl equivalent weight preferably is up to 100
and more preferably up to 75. The hydroxyl groups are preferably on
different carbon atoms. The chain extender more preferably is a
straight-chain compound in which the carbon atoms are bonded to the
terminal carbon atoms. Examples of chain extenders are ethylene
glycol, 1,2-propylene glycol, 1,3-propane diol, 1,4-butane diol,
1,6-hexanediol, diethylene glycol, triethylene glycol, dipropylene
glycol, tripropylene glycol, glycerin, trimethylol propane,
trimethylolethane, or an alkoxylate of any of the foregoing having
an equivalent weight of up to 125. Preferred among these are the
a,w-alkylene glycols such as ethylene glycol, 1,3-propane diol,
1,4-butane diol and 1,6-hexane diol. 1,4-butanediol is especially
preferred.
[0027] The microspheres consist of a shell, which encapsulates
either a vacuum or a gas. The shell is approximately spherical. It
defines a hollow space, which contains the encapsulated vacuum or
gas. The gas may be, for example, air, nitrogen, oxygen, hydrogen,
helium, argon, a hydrocarbon or other gas. The shell is capable of
withstanding the pressures encountered during the use of the
syntactic polyurethane elastomer. The shell may be, for example,
glass or other ceramic. The microspheres are generally of the
non-expandable type. Non-expandable types are preferred. The
microspheres may have a density of, for example, 0.1 to 0.6 g/cc.
The particle size preferably is such that at least 90 volume
percent of the microspheres have a diameter of 5 to 100 .mu.m,
preferably 10 to 60 .mu.m. Glass microspheres are preferred.
Suitable microspheres include commercially available products such
as 3M.TM. Microspheres from 3M Corporation and Expancel.TM.
microspheres from Akzo Nobel.
[0028] The microspheres constitute 5 to 50 weight percent,
preferably 15 to 30 weight percent of the reaction mixture and the
resulting syntactic polyurethane elastomer.
[0029] The prepolymer contains 3 to 12% by weight, preferably 6 to
12% by weight, isocyanate groups. The prepolymer is a reaction
product of at least one polyether polyol having a number average
hydroxyl equivalent weight of at least 1000 with an excess of an
aromatic polyisocyanate. The prepolymer may contain some amount of
the starting aromatic
[0030] The prepolymer/chain extender system of this invention may
cure more rapidly than conventional syntactic polyurethane
elastomer systems. If a slower cure is wanted or needed, some or
all of the isocyanate groups on the prepolymer may be blocked to
reduce their reactivity towards the chain extender. For example,
5-50% or 5-20% of the isocyanate groups can be blocked. Blocking is
achieved by reacting the prepolymer with a blocking agent; the
amount of blocking agent used corresponds to the proportion of
isocyanate groups to be blocked. Examples of blocking agents
include, for example, phenols such as phenol, bisphenol A azoles
such as 1,2,4-triazole, 2-methylimidazole, 3-methylpyrazole and
3,5-dimethylpyrazole; an oxime such as N-hydroxy succinimide,
cyclohexanone oxime, 4-methyl-2-pentanone oxime, methyl ethyl
ketone oxime; an amide such as .epsilon.-caprolactam,
N-methylacetamide, succinimide or acetanilide.
[0031] The hydroxyl equivalent weight of the polyether polyol(s)
used to make the prepolymer preferably is at least 1500 and is
preferably up to 3000.
[0032] The polyether polyol(s) used to make the prepolymer
preferably have a nominal functionality of 2 to 6, preferably 2 to
4 and more preferably 2 to 3. The polyether polyol(s) typically are
made by adding an alkylene oxide onto an initiator compound. The
"nominal functionality" of a polyether polyol refers to the average
number of alkoxylatable groups per molecule on the initiator
compound(s) used to make the polyether polyol. Actual
functionalities may be somewhat lower than nominal functionalities
in some instances.
[0033] Initiators that are useful for producing the polyether
polyol(s) include, for example, water, ethylene glycol, diethylene
glycol, triethylene glycol, 1,2-propane diol, dipropylene glycol,
tripropylene glycol, glycerin, trimethylolpropane,
trimethylolethane, pentaerythritol and other aliphatic polyalcohols
having a hydroxyl equivalent weight up to about 400. Primary and
secondary amines are also useful initiators, but may cause the
polyols to be more reactive than desired, so hydroxyl containing
initiators are preferred.
[0034] A preferred polyether polyol is prepared by adding propylene
oxide and ethylene oxide to a difunctional or trifunctional
initiator to produce a polyol having a hydroxyl equivalent weight
of 1500 to 2500, especially 1800 to 2200, and containing 5 to 30%
by weight polymerized ethylene oxide. The polymerized ethylene
oxide may be randomly polymerized with the propylene oxide, may
form one or more internal blocks and/or, most preferably, may form
terminal blocks that result in primary hydroxyl groups.
[0035] An especially preferred type of polyether polyol is made by
homopolymerizing propylene oxide or randomly copolymerizing 75-99.9
weight percent propylene oxide and 0.1 to 25 weight percent
ethylene oxide onto a trifunctional initiator, and optionally
capping the resulting polyether with up to 30% by weight (based on
total product weight) ethylene oxide to form a polyether polyol
having an equivalent weight of at least 1000 and up to 60, more
preferably up to 50, microequivalents of terminal unsaturation per
gram of polyol. This polyol preferably has an equivalent weight of
1000 to 3000, especially 1500 to 2500.
[0036] The aromatic polyisocyanate used to make the prepolymer may
be, for example, m-phenylene diisocyanate, 2,4- and/or 2,6-toluene
diisocyanate (TDI), the various isomers of
diphenylmethanediisocyanate (MDI), naphthylene-1,5-diisocyanate,
methoxyphenyl-2,4-diisocyanate, 4,4'-biphenylene diisocyanate,
3,3'-dimethoxy-4,4'-biphenyl diisocyanate,
3,3'-dimethyldiphenylmethane-4,4'-diisocyanate,
4,4',4''-triphenylmethane triisocyanate, polymethylene
polyphenylisocyanates, hydrogenated polymethylene
polyphenylisocyanates, toluene-2 ,4, 6-triisocyanate, and
4,4'-dimethyl diphenylmethane-2,2',5,5'-tetraisocyanate. Preferred
polyisocyanates have an average of 1.9 to 2.3 isocyanate groups per
molecule, especially from 2 to 2.2 isocyanate groups per molecule
and an isocyanate equivalent weight of 125 to 200. The aromatic
polyisocyanates may contain uretondione, uretonimine, isocyanurate,
biuret, allophonate, carbodiimide, urethane or urea linkages.
[0037] Especially preferred polyisocyanates are diphenylmethane
diisocyanate (MDI), including the 2,4'-, 2,2'- and 4,4'-isomers or
mixtures of two or more of such isomers, "polymeric" MDI products
which include a mixture of MDI and one or more polymethylene
polyphenylisocyanates, and modified MDI product that contain
uretondione, uretonimine, isocyanurate, biuret, allophonate,
carbodiimide, urethane or urea linkages and have an isocyanate
equivalent weight of 130 to 200.
[0038] The prepolymer is present in the reaction mixture in an
amount sufficient to provide an isocyanate index of 80 to 130. A
preferred isocyanate index is 90 to 125, and a still more preferred
isocyanate index is 90 to 115.
[0039] The catalyst is a non-mercury catalyst, by which is meant a
catalyst that does not contain mercury compounds other than
possibly as a trace impurity (constituting no more than 0.1% by
weight of the weight of the catalyst). The catalyst (and the amount
used) preferably is selected to provide a slow initial reaction for
a period of 1 to 10 minutes, followed by an accelerated cure. The
catalyst may be a thermally activated type, such as an encapsulated
or blocked type.
[0040] Various types of amines and metal urethane catalysts are
useful, including, for example, certain tertiary phosphines such as
a trialkylphosphine or dialkylbenzylphosphine; chelates of metals
such as Be, Mg, Zn, Cd, Pd, Ti, Zr, Al, Sn, As, Bi, Cr, Mo, Mn, Fe,
Co and Ni; metal salts of strong acids, such as ferric chloride,
stannic chloride, stannous chloride, antimony trichloride, bismuth
nitrate and bismuth chloride; strong bases, such as alkali and
alkaline earth metal hydroxides, alkoxides and phenoxides;
alcoholates or phenolates of various metals, such as Ti(OR).sub.4,
Sn(OR).sub.4 and Al(OR).sub.3, wherein R is alkyl or aryl, and the
reaction products of the alcoholates with carboxylic acids,
beta-diketones and 2-(N,N-dialkylamino)alcohols; alkaline earth
metal, Bi, Pb, Sn or Al carboxylate salts; and tetravalent tin
compounds, and certain tri- or pentavalent bismuth, antimony or
arsenic compounds. Also useful are blocked amine catalysts as
described in WO 2013/04333, copper catalysts as described in WO
2012/06263, zinc catalysts as described in WO 2012/06264, and
substituted bicyclic amidine catalysts as described in WO
2013/002974.
[0041] A preferred catalyst is a zinc carboxylate catalyst. The
zinc carboxylate catalyst is a zinc salt of a carboxylic acid. The
carboxylic acid is preferably a monocarboxylic acid having 2 to 24,
preferably 2 to 18, more preferably 6 to 18 and especially 8 to 12,
carbon atoms. A mixture of carboxylates may be present.
[0042] All or a portion of the zinc carboxylate catalyst may engage
in a rearrangement to form species which contain Zn--O--Zn
linkages. These species are considered as zinc carboxylates for
purposes of this invention.
[0043] The preferred zinc carboxylate catalyst may be used by
itself or in combination with one or more other metal carboxylate
catalysts. The other metal may be, for example, a group 3-12 metal
other than mercury. The zinc carboxylate preferably constitutes at
least 90 weight percent, at least 99 weight percent or at least
99.9 weight percent of such a mixture. A particularly useful
catalyst mixture is a mixture of 98-99.99 weight percent of one or
more zinc carboxylates and 0.01 to 2 weight percent of one or more
zirconium carboxylates. Such a mixture may contain small amounts
(up to 5 weight percent, more preferably up to 0.5 weight percent
and even more preferably up to 0.01 weight percent) of other metal
(other than mercury, zinc or zirconium) carboxylates.
[0044] The amount of zinc carboxylate catalyst may be 0.01 to 1
part, preferably 0.01 to 0.5 part and more preferably 0.01 to 0.2
parts per 100 parts by weight polyether polyol.
[0045] In some embodiments, no mercury-containing catalyst,
nitrogen-containing catalyst, tin catalyst, or other catalyst for
the reaction of polyol groups with isocyanate groups is present.
The reaction mixture is also essentially devoid of mercury
compounds, preferably containing no more than 0.01 weight percent
mercury, more preferably containing no more than 0.001 weight
percent mercury.
[0046] Upon curing, the microspheres become embedded in a
polyurethane matrix that forms in the curing reaction. Apart from
the presence of the microspheres themselves, the polyurethane
matrix is preferably non-cellular, as a cellular material becomes
easily crushed under high submarine pressures. Accordingly, the
reaction mixture preferably has at most very small quantities (such
as up to 0.5% by weight in total) of water or other chemical or
physical blowing agent. Preferably, physical blowing agents and
chemical blowing agents other than water are not added into the
reaction mixture. Commercially available polyether polyols often
contain small amounts, such as up to 0.25 weight percent, of water,
and this water may be carried into the reaction mixture with the
polyether polyol(s). Other starting materials may contain similarly
small amounts of water. It is preferred, however, not to add water
in addition to that (if any) carried in with the raw materials and
it is in any case preferred that the reaction mixture contains no
more than 0.25 weight percent water, preferably no more than 500
parts per million water, based on the entire weight of the reaction
mixture.
[0047] Moreover, it is preferred to include one or more components
that function to help prevent foaming. One such component is a
water scavenger, i.e., a material that adsorbs or absorbs water or
otherwise ties up any water as may be present and thereby reduce
the ability of that water to react with isocyanates during the
curing reaction. Zeolites, molecular sieves, fumed silica and other
desiccants can be used for this purpose. An anti-foam agent of
various types can be used. The anti-foam agent acts to destabilize
any gas bubbles as may form in the reaction mixture and cause them
to collapse. Water scavengers and anti-foam agents are typically
used in small amounts, such as 0.1 to 5 parts by weight per 100
parts by weight of the polyether polyol.
[0048] The reaction mixture may contain one or more
isocyanate-reactive materials in addition to the chain extender and
the polyether polyol described above. However, such
isocyanate-reactive materials, if used at all, are preferably used
in small amounts, such as up to 5 parts by weight total per 100
parts by weight of the chain extender. Examples of additional
isocyanate-reactive materials of this type include one or more
polyols having an equivalent weight of up to about 3000. Among
these are polyether polyols as described above with respect to
making the prepolymer. Other isocyanate-reactive materials that may
be present include polyester polyols, polyether polyols having
equivalent weights of 250 to 1000, crosslinkers (compounds having 3
or more hydroxyl groups or 1 or more primary or secondary amino
groups and an equivalent weight of up to 250), and the like.
[0049] Other optional ingredients include epoxy resins, particulate
fillers (in addition to the microspheres), fibers, reinforcing
agents, colorants, biocides, preservatives and antioxidants.
Fillers, fibers and reinforcing agents may be used in weights up to
200 parts per 100 parts by weight polyether polyol, but preferably
are used in small quantities, such as up to 50 parts or up to 20
parts by weight per 100 parts by weight polyether polyol, and may
be omitted entirely. Colorants, biocides, preservatives and
antioxidants preferably are used in very small quantities, such as
up to 5 or up to 2 parts by weight per 100 parts by weight
polyether polyol, if used at all.
[0050] Another optional ingredient is a .beta.-diketone compound.
The .beta.-diketone is a compound in which two keto groups are
separated by a methylene group, including compounds having the
structure:
##STR00001##
wherein each R is independently hydrocarbyl or inertly substituted
hydrocarbyl. Preferably, each R is independently an alkyl group,
which may be linear, branched or cyclic, which may by
aryl-substituted or otherwise inertly substituted. More preferably,
each R is independently an alkyl group (linear, branched or cyclic)
having 1 to 8, especially 1 to 4 carbon atoms.
[0051] Examples of .beta.-diketone compounds are acetylacetone
(pentane-2,4-dione), hexane-2,4-dione, heptane-3,5-dione,
2,2,6,6-tetramethyl-3,5-heptanedione, and the like.
[0052] The presence of a .beta.-diketone compound has been found to
improve the bond between multiple sections of the syntactic
polyurethane elastomer, when such sections are formed sequentially
as described below. The bond strength is in some cases increased
very substantially when the .beta.-diketone compound is present.
Additionally, when the .beta.-diketone compound is included in the
reaction mixture, the bond line, when visualized microscopically at
a magnification of 100.times., is often seen to have fewer defects,
compared to when the .beta.-diketone compound is not present in an
otherwise identical formulation, to the point that no defects are
visible under such magnification. The bondline in some cases is no
longer visible under such magnification. This effect is seen
especially when the non-mercury catalyst is a zinc carboxylate
catalyst.
[0053] The .beta.-diketone compound may constitute, for example, at
least 0.05, at least 0.06, or at least 0.10 to 1% of the combined
weight of all components of the reaction mixture except the
polyisocyanate(s). In some embodiments, the .beta.-diketone
constitutes up to 0.5% or up to 0.25% of such weight. A preferred
amount is 0.06 to 0.5%. A more preferred amount is 0.10 to 0.25%
and a still more preferred amount is 0.1 to 0.2%, on the same basis
as before.
[0054] Alternatively, the amount of the .beta.-diketone compound
can be expressed in terms of the amount of non-mercury catalyst,
particularly when the non-mercury catalyst is a metal catalyst. The
weight of .beta.-diketone compound may be, for example, 1 to 10,
preferably 1 to 5, more preferably 2 to 5 and still more preferably
3 to 4 times that of the metal non-mercury catalyst(s).
[0055] Still another optional ingredient is an epoxy resin, which
may constitute, for example 1 to 15, preferably 3 to 10 and more
preferably 3 to 7 percent of the combined weight of all ingredients
except the polyisocyanate(s). The presence of the epoxy resin has
been found to produce smaller hard segment domains, which in turn
is believed to have a beneficial effect on the ability of the
syntactic polyurethane elastomer to adhere to itself. Epoxy resins
include, for example, glycidyl ethers of bisphenols, epoxy novolac
resins, epoxy cresol resins, and the like, especially those having
an epoxy equivalent weight of up to 500 or up to 250.
[0056] A syntactic polyurethane elastomer is formed by mixing the
various components and allowing them to cure. It is often
convenient to formulate the components into a polyol component
which contains the chain (and any other isocyanate-reactive
species, as may be present) and a separate isocyanate component
that contains the prepolymer. Other ingredients can be formulated
into either the polyol or isocyanate component, although it is
typical to formulate most or all of these into the polyol
component. To make the syntactic polyurethane elastomer, the polyol
component and isocyanate component are mixed at proportions
sufficient to provide an isocyanate index as indicated above, and
allowed to cure.
[0057] The components can be heated when mixed or mixed at ambient
temperature. Preheating can be to 30 to 100.degree. C., for
example. The components are generally cured in a mold; the mold can
be preheated if desired to a similar temperature. Heat can be
applied throughout the curing process if desired; but this is not
always necessary or desirable, as the curing reaction is
exothermic. If an elevated curing temperature is used, the elevated
temperature may be at least 60.degree. C., at least 80.degree. C.,
at least 100.degree. C. or at least 120.degree. C. Curing is
performed until the polyurethane has developed enough strength to
be demolded without permanent damage or distortion. Once demolded,
the syntactic polyurethane elastomer can be post-cured if
desired.
[0058] The cured syntactic elastomer includes a polyurethane matrix
formed in the curing action, in which the microspheres are
embedded. The content of microspheres will generally be essentially
the same as the content of microspheres in the reaction mixture. As
before, the polyurethane matrix preferably is non-cellular apart
from the presence of the embedded microspheres.
[0059] The invention has particular advantages in applications in
which multiple sections of the syntactic polyurethane elastomer are
applied to a substrate, such that the successively-applied sections
meet and form a bondline. In such embodiments, a first reaction
mixture as described herein is applied to the substrate and at
least partially cured to form a first section of syntactic
polyurethane elastomer. The curing in this step is continued until
the polymer has developed enough green strength to be demolded (if
in a mold) or otherwise to maintain its shape during subsequent
operations. Then, a second reaction mixture as described herein is
applied to the substrate and in contact with the first section of
syntactic polyurethane elastomer. This forms a bondline between the
first section of syntactic polyurethane elastomer and the second
reaction mixture. The second reaction mixture is then at least
partially cured to form the second section of syntactic
polyurethane elastomer adherent to the first section of syntactic
polyurethane elastomer. The bond strength at the bondline is
preferably at least 5 MPa, more preferably at least 6 MPA and still
more preferably at least 8 MPa, as measured by ASTM D638, modified
to use a test sample that contains the bondline.
[0060] The foregoing process can be extended to any number of
applied sections.
[0061] The individual sections may cover all or only a portion of
the substrate. The second and any successive sections may be
applied on top of the first section, to form a multilayer syntactic
polyurethane coating. Alternatively, the different sections may be
applied to adjacent portions of the substrate such that the
later-applied section(s) come into contact with one or more
earlier-applied section(s) to form a bondline. By "bondline", it is
meant the point or points at which the sections are in contact with
each other.
[0062] Pipelines (including subsea pipelines or land pipelines) and
subsea architecture are substrates of particular interest to this
invention. Such a substrate can be made of any material that is
suitable for its intended use, provided it can withstand the
temperatures of the polyurethane-curing process. Polymeric and
ceramic materials can be used to make the substrate, and these
materials can be reinforced if desired. The preferred materials of
construction for pipelines and subsea architecture are metals,
especially steel. The substrate may also be coated with a corrosion
inhibiting material, including, for example, fusion-bonded epoxy,
thermally-sprayed aluminum, a liquid-curable epoxy resin, and the
like, prior to being coated with thermal insulation.
[0063] The pipe segments may be, for example, 1 to 20 meters in
length, and 2 centimeters to 2 meters in diameter. The pipe
segments may have diameters of at least 10 centimeters or at least
15 centimeters, and may have diameters up to 1 meter, up to 0.5
meters or up to 0.35 meters. The insulation layer may be 1
centimeters to 25 centimeters thick. The ends of the pipe segments
may be flanged or otherwise adapted (via various fittings, for
example) to be joined to an adjacent pipe segment to produce a
joint between the adjacent pipe segments.
[0064] The pipe or undersea architecture may be linear or have a
more complex structure. It may be, for example, branched, curved or
have other non-linear configurations. It may have external features
that protrude partially or completely through the applied syntactic
polyurethane elastomer section(s). Another significant advantage of
this invention is that the syntactic polyurethane elastomer
section(s) are very resistant to cracking at or near branch points
and at or near sites at which protrusions partially or completely
through the layer(s). Prior to this invention, this performance has
been difficult to achieve without using mercury catalysts.
[0065] For pipe and undersea architecture applications, the
syntactic polyurethane elastomer may be applied in thicknesses of
2.5 to 20 cm, especially 5 to 12 cm. These thicknesses are usually
sufficient to provide the necessary thermal insulation.
[0066] The cured syntactic polyurethane elastomer consists of a
polyurethane matrix, which is preferably non-cellular, in which the
microspheres are dispersed. The polyurethane matrix may have a
morphology characterized by the presence of small discrete
morphological domains on the order of 0.1 to 3 .mu.m in diameter,
and the substantial absence of discrete morphological domains on
the order of 5 to 30 .mu.m in diameter. "Diameter" here refers to
the longest dimension, as the discrete morphological domains may
not be strictly spherical. The presence and measurement of these
discrete morphological domains can be seen using microscopic
methods such as atomic force microscopy (AFM) which are capable of
resolving features in the 100 nm to 100 .mu.m size range. FIGS.
2a), 2b) and 2c) are micrographs of a syntactic polyurethane
elastomer of this invention (FIG. 2a) and two prior art syntactic
polyurethane elastomers. In FIG. 2a), discrete morphological
domains 51 are seen to have diameters in the range of about 2
.mu.m. When a syntactic polyurethane elastomer is made using the
same ingredients (including the same catalyst) but without first
forming the prepolymer, large discrete morphological domains form.
In FIG. 2b) these large discrete morphological domains are
indicated by reference numerals 52. FIG. 2c) is a micrograph of a
conventional syntactic polyurethane elastomer made in a one-step
process using a mercury catalyst. This material is seen to have
similar morphology to this invention, in that discrete
morphological domains 53 are small, being mainly less than 1 .mu.m
in diameter. The discrete morphological domains are dispersed in a
continuous phase indicated generally in each of FIGS. 2a), 2b) and
2c) by reference numeral 54. The continuous phase is believed to
consist mainly of polyether chains from the polyether polyol
starting material.
[0067] On dynamic mechanical analysis, the syntactic polyurethane
elastomer of this invention may exhibit a pronounced tan .delta.
peak centered in the temperature range of 30 to 100.degree. C. Tan
.delta. at the maximum of this peak typically has a value of 0.15
to 0.3, more typically about 0.175 to 0.25. In FIG. 1, this peak on
tan .delta. curve 41 is indicated by reference numeral 44. The tan
.delta. curve often passes through a maximum in the range of
-100.degree. C. to -30.degree. C. (FIG. 1, reference numeral 42),
which is believed to represent the glass transition of a rubbery
phase corresponding to the polyether polyol. The tan .delta. then
goes through a minimum centered at about -30.degree. C. to about
10.degree. C. (FIG. 1, reference numeral 43), followed by the
pronounced tan .delta. peak centered at 30 to 100.degree. C. This
maximum is then followed by another minimum centered above
100.degree. C. (FIG. 1, reference numeral 45). Yet another maximum
appears at temperatures greater than 150.degree. C. (FIG. 1,
reference numeral 46). This last maximum is believed to correspond
to the glass transition of hard segment.
[0068] The maximum centered at 30 to 100.degree. C. is believed to
correspond to a relaxation of a partially or imperfectly ordered
rigid phase, in which the hard segment (corresponding to domains
rich in the reaction product of chain extender) is somewhat mixed
with soft segment (i.e., the polyether chains brought into the
polymer via the prepolymer).
[0069] DMA curves are conveniently obtained on 1-mm thick samples,
using a strain-controlled rheometer such as an ARES 2000 rheometer
manufactured by TA Instruments at an oscillation frequency of
6.2832 radians/second and a temperature ramp of 3.degree. C. per
minute over a temperature range of -100.degree. C. to 200.degree.
C.
[0070] The following examples are provided to illustrate the
invention, and are not intended to limit the scope thereof. All
parts and percentages are by weight unless indicated otherwise.
EXAMPLE 1 AND COMPARATIVE SAMPLES A AND B
[0071] Polyol A is a nominally trifunctional polyether made by
adding propylene oxide and then ethylene oxide to a trifunctional
initiator. Polyol A contains about 15% ethylene oxide by weight. It
contains mainly primary hydroxyl groups and has a hydroxyl
equivalent weight of about 2050.
[0072] The Zn/Zr catalyst is a mixture of zinc and zirconium
carboxylates in which the weight ratio of zinc to zirconium is
99-99.5:0.5-1. The catalyst contains some species having M-O-M
linkages, wherein M stands for the metal, i.e. either Zn or Zr.
[0073] The microspheres are 3M grade S38HS glass microspheres.
[0074] Polyisocyanate A is a modified MDI having an isocyanate
equivalent weight of 160 g/mol and an isocyanate functionality of
about 2.
[0075] Polyurethane Elastomer Example 1 is made as follows: 62.5 g
of Polyol A is reacted under nitrogen with 45.5 g Polyisocyanate A
until the isocyanate content is reduced to about 8% by weight.
Glass microspheres, yellow pigment, catalyst and antifoam are added
to pre-polymer in amounts as set forth in Table 1.
TABLE-US-00001 TABLE 1 Ingredient Parts by weight Prepolymer 325.6
Zn/Zr Catalyst/Acetylacetone 0.10/0.4 Antifoam 0.06 Glass
microspheres 73.2 Pigment 0.64
[0076] 400 parts of the prepolymer mixture is then mixed with 30.9
parts of 1,4-butandiol. A portion of the resulting mixture is case
into a mold preheated to 50.degree. C. and cured at that
temperature in the mold for 2 hours. A sample is taken to
microscopy. A micrograph of the sample forms FIG. 2a). As can be
seen in FIG. 2a), the sample contains small discrete morphological
domains 51 but no large ones, similar to those of the
mercury-catalyzed elastomer as shown in FIG. 2c). Another sample is
evaluated by DMA using an ARES 2000 rheometer operated at an
oscillation frequency of 6.2832 radians/second, and a temperature
ramp of 3.degree. C./minute over the temperature range -10 to
200.degree. C. The DMA curve is shown in FIG. 1. A tan .delta. peak
having a value of over 0.2 is centered at about 30.degree. C.
[0077] Comparative Sample A is made using the same ingredients as
used to make Example 1, except all the ingredients are reacted at
once instead of first forming a prepolymer from the polyol and
polyisocyanate. A micrograph of the resulting elastomer is shown in
FIG. 2b). In contrast to the Example 1 material, this elastomer has
very large discrete morphological domains. On DMA analysis,
virtually no peak is seen in the tan .delta. curve between 30 and
100.degree. C. The bond strength for Comparative Sample A is only
about 3.1 MPa.
[0078] Comparative Sample B is made in a one-step process using the
same ingredients, except the catalyst is an organomercury catalyst.
FIG. 2c) is a micrograph of this elastomer. It contains small
discrete morphological domains much like the Example 1 elastomer,
and lacks the large discrete morphological domains seen in
Comparative Sample A. On DMA, this material exhibits a prominent
tan .delta. peak centered at about 70.degree. C. At the maximum,
this tan .delta. peak has a value of about 0.175.
Specific Embodiments: In Specific Embodiments, the Invention is
[0079] 1. A cured syntactic polyurethane elastomer which is a
reaction product of a reaction mixture comprising an alkylene
glycol chain extender, 5 to 50 weight percent, based on the weight
of the reaction mixture, of microspheres, an isocyanate-terminated
prepolymer having an isocyanate content of 3 to 12% by weight, and
a non-mercury catalyst, wherein (i) the prepolymer is the reaction
product of at least one polyether polyol having a number average
hydroxyl equivalent weight of at least 800 with an excess of an
aromatic polyisocyanate, (ii) the amount of prepolymer provided to
the reaction mixture is sufficient to provide an isocyanate index
of 80 to 130, and (iii) the reaction mixture is essentially devoid
of mercury compounds.
[0080] 2. The preceding embodiment, wherein the cured syntactic
elastomer comprises a polyurethane matrix in which the microspheres
are embedded.
[0081] 3. Any preceding embodiment, wherein the cured syntactic
elastomer forms a coating on a substrate.
[0082] 4. A method for making a syntactic polyurethane elastomer,
comprising
[0083] a) forming a reaction mixture containing an alkylene glycol
chain extender, 5 to 50 weight percent, based on the weight of the
reaction mixture, of microspheres, an isocyanate-terminated
prepolymer having an isocyanate content of 3 to 12% by weight, and
a non-mercury catalyst, wherein (i) the prepolymer is the reaction
product of at least one polyether polyol having a number average
hydroxyl equivalent weight of at least 800 with an excess of an
aromatic polyisocyanate, (ii) the amount of prepolymer provided to
the reaction mixture is sufficient to provide an isocyanate index
of 80 to 130, and (iii) the reaction mixture is essentially devoid
of mercury compounds, and
[0084] b) curing the reaction mixture to form the syntactic
polyurethane elastomer.
[0085] 5. Any preceding embodiment wherein the reaction mixture
contains 15 to 25 weight percent microspheres.
[0086] 6. A process for producing a substrate having an applied
syntactic polyurethane elastomer, comprising
[0087] a) forming a section of a syntactic polyurethane elastomer
on at least a portion of the substrate by (1) applying a first
reaction mixture containing an alkylene glycol chain extender, 5 to
35 weight percent, based on the weight of the reaction mixture, of
microspheres, an isocyanate-terminated prepolymer having an
isocyanate content of 3 to 12% by weight, and a non-mercury
catalyst, wherein (i) the prepolymer is the reaction product of at
least one polyether polyol having a number average hydroxyl
equivalent weight of at least 800 with an excess of an aromatic
polyisocyanate, (ii) the amount of prepolymer provided to the
reaction mixture is sufficient to provide an isocyanate index of 80
to 130, and (iii) the reaction mixture is essentially devoid of
mercury compounds, to at least a portion of the substrate and (2)
at least partially curing the first reaction mixture to form the
first section of syntactic polyurethane elastomer, and then
[0088] b) forming a second section of syntactic polyurethane
elastomer on at least a portion of the substrate by (1) applying a
second reaction mixture containing an alkylene glycol chain
extender, 5 to 35 weight percent, based on the weight of the
reaction mixture, of microspheres, an isocyanate-terminated
prepolymer having an isocyanate content of 3 to 12% by weight, and
a non-mercury catalyst, wherein (i) the prepolymer is the reaction
product of at least one polyether polyol having a number average
hydroxyl equivalent weight of at least 800 with an excess of an
aromatic polyisocyanate, (ii) the amount of prepolymer provided to
the reaction mixture is sufficient to provide an isocyanate index
of 80 to 130, and (iii) the reaction mixture is essentially devoid
of mercury compounds to at least a portion of the substrate and in
contact with the first section of syntactic polyurethane elastomer
to form at least one bondline between the first section of
syntactic polyurethane elastomer and the second reaction mixture
and (2) at least partially curing the second reaction mixture to
form the second section of syntactic polyurethane elastomer
adherent to the first section of syntactic polyurethane
elastomer.
[0089] 7. Embodiment 6, wherein the bondline has a bond strength of
at least 8.0 MPa.
[0090] 8. Embodiment 6, wherein the bondline has a bond strength of
at least 8.0 MPa.
[0091] 9. Any of embodiments 6-8, wherein the bondline is not
visible under a magnification of 100.times., and/or has no visible
defects when visualized microscopically at a magnification of
100.times..
[0092] 10. Any of embodiments 3-9, wherein the substrate is a pipe
(for subsea or land use) or undersea architecture.
[0093] 11. Embodiment 10, wherein the a pipe (for subsea or land
use) or undersea architecture is branched, curved or has another
non-linear configuration.
[0094] 12. Embodiment 10 or 11, wherein the a pipe (for subsea or
land use) or undersea architecture has one or more external
features that protrude partially or completely through the applied
syntactic polyurethane elastomer.
[0095] 13. Any preceding embodiment, wherein the polyether polyol
used to make each respective isocyanate-terminated prepolymer is
prepared by (A) adding propylene oxide and ethylene oxide to a
difunctional or trifunctional initiator to produce a polyol having
a hydroxyl equivalent weight of 1500 to 2500 and containing 5 to
30% by weight polymerized ethylene oxide, wherein the polymerized
ethylene oxide is randomly polymerized with the propylene oxide,
forms one or more internal blocks and/or forms terminal blocks that
result in primary hydroxyl groups or (B). homopolymerizing
propylene oxide or randomly copolymerizing 75-99.9 weight percent
propylene oxide and 0.1 to 25 weight percent ethylene oxide onto a
trifunctional initiator, and optionally capping the resulting
polyether with up to 30% by weight (based on total product weight)
ethylene oxide to form a polyether polyol having an equivalent
weight of 1500 to 2500.
[0096] 14. Any preceding embodiment, wherein the chain extender is
1,4-butanediol.
[0097] 15. Any preceding embodiment, wherein the non-mercury
catalyst is a zinc carboxylate or a mixture of 98-99.99 weight
percent of one or more zinc carboxylates and 0.01 to 2 weight
percent of one or more zirconium carboxylates.
[0098] 16. Any preceding embodiment, wherein each respective
reaction mixture contains 15 to 25 weight percent microspheres.
[0099] 17. Any preceding embodiment, wherein the reaction mixture
contains a .beta.-diketone compound.
[0100] 18. Embodiment 17, wherein the .beta.-diketone is a compound
having the structure:
##STR00002##
wherein each R is independently hydrocarbyl or inertly substituted
hydrocarbyl.
[0101] 19. Embodiment 18, wherein each R is independently a linear,
branched or cyclic alkyl group having 1 to 4 carbon atoms.
[0102] 20. Embodiment 17, wherein the .beta.-diketone compound is
one or more of acetylacetone (pentane-2,4-dione), hexane-2,4-dione,
heptane-3,5-dione and 2,2,6,6-tetramethyl-3,5-heptanedione.
[0103] 21. Any of embodiments 17-20, wherein the non-mercury
catalyst is one or more metal catalyst(s), and the weight of the
.beta.-diketone compound 1 to 10 times that of the metal
non-mercury catalyst(s).
[0104] 22. Embodiment 21, wherein the non-mercury catalyst is one
or more metal catalyst(s), and the weight of the .beta.-diketone
compound 2 to 5 times that of the metal non-mercury
catalyst(s).
[0105] 23. Embodiment 21, the non-mercury catalyst is one or more
metal catalyst(s), and the weight of the .beta.-diketone compound 3
to 4 times that of the metal non-mercury catalyst(s).
[0106] 24. Any preceding embodiment, wherein the reaction mixture
contains at least one water scavenger.
* * * * *